Tunnel kiln



Feb. 3. 1 925.

W. E. HINSDALE TUNNEL KILN 5 sheds-sheet 1 Filed Feb. 17, 1921 INVENTORBy Attorneys,

Gagw,

Feb. 3. 1925. 1,525,130

w. E. HlNsDALE TUNNEL KILN Filed Feb. 17, 1921 5 Sheets-Sheet 2 Feb. 3.1925.

` w. E. HINSDALE TUNNEL KI LN By Attorneys,

am@ L OMA y INVENTOR Feb. s. 1925. 1,525,130 w. E. HINSDALE l TUNNELKILN Filed Feb. 17, 1921 5 Sheets-Sheet 4 INVENTOR 1 @Md/L@ By AHorneys,

'Fem 3.1925 1,525,130

W. E. Hl NSDALE TUNNEL KILN Filed Feb. 17, 1921 5 ShetS-Shet 5 Fb@ J4.

INVENTOR is? By Attorneys,

Patented Feb. 3, 1925. A

UNITED STATES PATENT OFFICE.

TUNNEL KILN.

Application led February 17, 1921.

articles or materials to be subjected to heat' treatment are loaded onsuitable cars and caused to progress contlnuously or intermittentlythrough a tunnel chamber. In such kilns, it is customary to divide thestructure longitudinally into three sections, of usually unequal length,the first section being that in which the material under treatment isfirst warmed and then pre-heated, this portion of the kiln beingdesignated the heating or heating-up zone; the intermediate section,wherein vthe heat treatment is performed, will be herein referred to asthe torridzone; the final section, in which the articles or materials,after heat treatment, are gradually cooled, is designated the cooling orcooling-01T zone.

Tunnel kilns have heretofore been of two types; namely, those in whichdirect combustion'has been maintained in the tunnel chamber, so that theire gases or products of combustion have come into direct contact withthe wares. or materials under treatment; and those of the muiile type,in which a thin inutile wall or partition has enclosed the tunnelchamber and separated it` from the adjacent chambers or flues in whichthe combustion occurs, and wherein circulate the fire gases or productsof combustion.

The present invention provides improved constructions of tunnel kilns,its object being to avoid certain disadvantages heretofore inherent inkilns of this type, and to improve the eiciency, economy, certaint ofoperation, and ease of control of such kilns. More specifically, it aimsto combine the advantages of both the combustionchamber type and-muletype 4or tunnel kilns, and produce such a kiln which, among other uses,shall be practicable and advantageous for the burning of chinaware,porcelain and other earthenware, while avoiding the necessity ofenclosing such wares in the usual saggers or protecting boxes forsealing the Serial No. 445,827.

ware from the action of gases that may be present in the kiln. Otherimportant ob- ]ects are to secure continuous operatior of the k1ln, toprovide for ready inspectica of the interior parts during operation, toprovide for repairs without lnecessitating the cooling down of the kiln,so as to avo'.`d loss of goods undergoing treatment at the time when.repairs become necessary, to insure durablhty of the members orelements of the tunnel, by enabling them to 'endure changes oftemperature in heating or vcooling, to provide for vmaintaining avsubstantially fixed atmosphere within the torrid zone, whilemaintaining a continuous but slow circulation of air through the tunnelfor the removal of super-heated vapor given ol" from the advancing waresprevious to their entering into the torrid Zone, and for enablingefficient control to be maintained of the temperature in the torridzone, as well as of ,the duration vof time during which the goods areexposed to such temperature.

Toattain these advantages, the invention provides certain improvedconstructions, the nature of which -will be developed as the descriptionproceeds. One important feature is the provision for heating the kilnelectrically, by means of successive electric furnace units which maybeindividually' inspected and controlled from the exterior, and which,inr case of need, may be individually removed and replaced withoutinterrupting continuity of the heat treatment in the kiln.

In the accompanying dra-Wingspaplan is given in Fig. l and the otherlongitudinal views are divided into three equal portions, designated,respectively as Figs. 2, 2a, 2b, etc., of which the first in eachstance covers the entering portion of the kiln, in traversing which thegoods are preheated;the second includes the torrid zone and more or lessof the pre-heating zone and the initial portion'l of the cooling zone;and the third includes the major portion of the cooling4 Zone, leadingto the exit or emerging end of the-tunnel.

Figure l, is a plan of the tunnel kiln. Figs. 2, 23 and 2b are avertical longitudinal mid-section thereof.

Figs. 3, 3a and 3b are a longitudinal horizontal section, thev plane ofwhich through `the torrid zone, is indicated by tie line 3* in Fig. 14.

in; g

Figs. 4, 42l and 4" show the the kiln in side elevation.

Fig. is an end view or elevation of the entering end.

Fig. 6 is a! transverse section on the line 6-6 of Fig. 3.

Fig. 7 is a transverse section on the line 7-7 of Fig. 3. Fig. 8 is atransverse section, in the plane of line 8 8 in Fig. 3.

Fig. 9 is a transverse section, on line 9 in Fig. 3.

Fig. 10 is a transverse section, on line l. in Fig. 3a.

Fig. 11 is a transverse section on the line 11-11 in Fig. ab.

' .'Figf12 is a transverse section on the line 12-.12 .in Fig. ab.

Fig. 13 is an elevation of the outlet on emerging end of the kiln.

Of the foregoing views, Fig. 1 is on a greatly reduced scale. Figs. 2-4are on a larger scale, Figs. 5 and 13 are on an intermediate scale, andFigs. 6-12 are on a still larger scale.

Fig. 14 is a transverse section through the torrid Zone, on the line14-14 in Figs. 3 and4, the electric furnace at the right being shown initsl operative position, and that at the left removed for repairs; theview being on a larger scale than Figs. 6-12.

In the several views, the same reference letters or figures designatethe same or corresponding parts, throughout.

In generah the kiln is built at its ends with an outer shell of iron orsteel plate, suitably strengthened by ribs, and, in the central portionexposed to heat, is constructed of suitable refractory material, withopen-y ings formingl dead air spaces or fines, as will be described. indetail. The tunnel chamber has track rhils laid through itlongitudinally, on which may travel the cars or platfrm's'ccarrying thematerial under treatment. At the entering end and at the outlet oremerging end are doors which may be closed in a nearly air-tight manner,after the introduction and discharge of successive cars.

Referring to the drawings, A designates the tunnel chamber, closednormally by a door a. at its entering end and by a door b at its outletor emerging end. The wares are carried through. on cars B, of anysuitable construction, having, as usual, a refractory bed or hearth,which, in use, forms the bottom of the tunnel chamber. The constructionshown in Fig. 14 will serve as a suitable illustration of the cars, oneof which is shown at B in Fig. 2a. In both these figures, the dottedoutline r indicates the extreme dimension of the stack of goods or warescarried by the car, and very nearly filling the tunnel chamber A. Thehearth portions of the successive cars fit together so as to form acontinuous union.

The tunnel kiln is divided into a succession of 4sections or zones,which may differ in construction, as will now be described:

Of these zones, C is the first warming zone; D the second warming zone;E.the pre-heating zone; F the tiring or torrid zone; G the rst cooling`zone; H the second cooling zone; and J the iinal cooling zone, adjacentthe outlet The first warming zone C is Shown in Figs. 1-4 and the leftof Fig. 6. The portion C of the tunnel chamber A forms the inlet chamberof the tunnel. The construction of this zone is-shown as having sidewalls 20 of iron, which may be formed of cast-iron plates or sectionsbolted together with their flanges preferably on the inside, the betterto interfere with any air currents that may seek to' fiow between thestacks of wares and the chamber wall, thus breaking .up such currentsand forcing them towards and through the wares. The roof 21 is bestconstructed by crossingthe chamber with ordinary T-irons and bridgingthe spaces between with -ordinary flat arch hollow tiles. This style ofroof prevents too rapid absorption of heat and gives economy ofconstruction.

The second warming Zone D, which encloses a section D of the tunnelchamber A, is shown in Figs. 1-4 and the right of Fig. -G. Theconstruction shown is the same as that of zone C, except that the walls22 are double, being spaced Vpreferably about 6 apart, so as to enclosebetween them an air space or flue 23. At the entering end of zone D, theflues 23 on opposite sides open upwardly into an air box 24, Fig. 4,forming within it a cross-over flue 25, Figs. 2 and 6, whichcommunicates with'the inlet of an exhaust fan 2G, the purpose of whichis to exhaust the air from the air fiues 23 between the walls onopposite sides of the tunnel chamber. A.

Underlying zones Gand D, is a continuous foundation 29, Fig. 2, havingside walls 30, which underlie the iron panel walls 20, 22. .These ironwalls are at one end firmly secured to the foundation ofthe first panelor panels nearest the pre-heating zone E, while the remainder of theiron work of these zones is free to expand longitudinally on suchsupporting base. For this purpose, the flanges of the cast iron platesmay be united by bolts engaging enlarged or slotted bolt holes. as iscommon.

The pre-heating zone E is shown partly in Figs. 1-4 and partly in Figs.2a-4a, and in the cross-sections Figs. 7 and 8.

The enclosed portion of the tunnel chamber A in zone E is lettered E. Inthis portion E of the tunnel chamber, the wares are progressivelypre-heated as they approach the torrid zone. This pre-heating zone E isconstructed with. an exterior shell or casing 32, of brick or tilemasonry, suitably stiffened or reinforced by vT-iron vribs orv loads ofstacks or wares earriedby the car platforms orfhearths, and the-waresare stacked 'to a height :to barelypass through the tunnel with safety.'By reason thereof,

the successivecarloads of wares form, in efother framing 33. Towardthe-hotter end,

i fectfa Yfairly tight closure or stopper for a refractory ning 35:-isprovided, which may be made up of refractory brick Ortner-substantiallypreventing the flow 'of :air be- The `roof of zone E lis builtiofmasonry in tween the stacks of wares and the inner arch'form, the thrustofthe arch "being walls of .the tunnel chamber. This conditaken up bylateral members 36 of the metal tion continues until theV zone-E isreached,

Jframing, these .being shown as T-irons tying wherein the chamber E isabruptlyl widened' 1 f horizontallyH between the extended upper- (seeFig. 3), so that the advancing oarloids" .endsof the upright side-frames 33.- 1 The of wares enter'into a wider tunnel chamber,

masonry arch 3 has a lining 38 covering the which chamber, however, isetfectually .shut

bers C and D',

As the metal construction of zones C and; and wares illin D, andthemasonry Aconstruction otzone E, v '.1'he`inner re actory lining havedifferent ratios of expansion,` and the hotter part o f the tunne.tinuation of the side linings 35. by

t ese chambers.'

chamber E -these zones are subjected to ywidely dissimiis free to expandlongitudinally independlar temperatures, an' 'exglansion jointis entlyof the outerv wall, as ithas no abutment Y formed at the junction ozones D and E. therewith, except where .the walls are wid- For urpose,the masonryvwalls 32, 34 lened at 51 (Fig. 3") ad'acent to the entranceare exten ed so as tooverlap the end porto the firing chamber of thetorrid zone. tion of the zone D, being extended inward at 40 to meet theouter wall 22, and rated from the preheating chamber by a hotterlongitudinal portion, forminga cono from the first and second'warmincham.A

the presence of t e cars The tiring chamber F is partiall. sepa- 3 5,enclosing an inwardly extending pier 41 on eaclrsrde, contraction-rinthe wall at 52.v vThis conwhichmeetstheextended portion 22 of thetracted portion 'constitutes a portalto the w" inner wall of, 'the zoneD. The. contact befillng Gham'bel'- Th Walls' 0f this portal tween theportions orY piers- 40, 41, and the 'are locatedfto -form a tunnelopening of 'respective walls of zone D, is a sliding corrpreferably thesame dimensions as the walls tact, so that either section of thestructure of the chambers Cf D, aifording'as'close an' may slide'longitudinallywith diiferences of approach as is practicable to ftheload or "tern rature.- stack of wares (win Fig.'14), so asto form T epiers' 40 and 41 are longitudinally a partial seal around the'stacksofwares for separated (by preferably about slx feet) to obstructing, theHOW '0f 'air 'Passing' them; form on each side anintervening chamber Inthis manner, vthe tiring chamber is. apor air space 42; and the piers40,A 41 areexproximately shut oi from the-.preheatng `tended overthetop, as'sh'own'- in Fig.- 2', chamber.-

forming larches 40', 41", the structure being n Y 'An expansion joint isformed between .the

icov

` extended upwardly at 43 and formin over tunnel walls ofthe preheatingzone E and v.

thetop, an extended flue or air cham r 44, firing zone F, beingconveniently formed asv .shown in Fig.l 2. These air chambers betweenthe portal 52 andthe expanded por- 23, 23. Extended through theremainder-of pansion .joint is formed by one wall overlapthe zone E, oneach side of the tunnel champing the other with a sliding. lit admittingber E,-are arranged hot air pipes 5:0,y of of expansion or contraction.'In the con'- suitably refractory material, such as cast structionshown, the portal wall is' made rightl stacks, as shownin Figs. and 8v.-The embrace the end portion ofthe wall'l, -ends of these plpes arecarried through the while the inner wall 54 is extended inside piers 41,and open freely into lthechambers thereof in such manner ,as to form acham;

42, so that the hot air may flow fr omthem ber or liue 55l extendingvertically vin each l into these chambersand thence through the sidewall, these lilies bem Connected by an r.; lateral air lines 23. Thetotal capacity of operhead flue,56 (F ig.l 2a The side.. flues the pipes50 should approximately equal 55' open into the ends of the radiatorpipes .42,44 communicate freely withthe airiiues tion 51, as shown inFigs. 2*, 3a.- 'I'his ex iron, these pipes being superposed inupdouble,- an outer wall 53 being formed to that of the tlues 23. Thepipes 50 on oppo- 50 on one side, and, on the other side, open p sitesides. of the tunnel chamber converge into longitudinal llues 57 (shownin dotted slightlyas the carloads of Wares advance, lines Ain Fig. 28)these fines being extended,

being carried inside ofthe linings 35; through theside walls of the'torrid zone/F The walls 20 of the zone C andthe conof the tunnel kilnstructure.

tinuing walls of the zone D,\are equally The construction of thisportion ,of the spaced apart, so that the tunnel chambers structure isshown -in cross section in Fig.

C, D are of uniform width, this width be- 9, a transverse arched chamber,58 ybein ing barely sutliclent to safelyv enclose the formed at eachside, in order teprovide su ficient lengthfor the portal 52, whileavoid-l ing too massive masonry. At the opposite or outgoing end of thefiring chamber F", the -structure is formed with a substantialduplication cf the portal 52, the second portal being marked 62, andhaving the same structure already described; that is to say, the sideflues and overhead flue 56'are duplicated, these flues being marked and66, respectively, and the longitudinal iues 57 .open in to these flues65. A

The' portals 52 and 62 are each'of a length equalling approximately thelength of one of the cars B, and are formed with refractory inner wallsand with suitable masonry outer walls, and overhead arch, as sliowninFig.'

9. Thus, the overhead portion of each ort'al has an inner refractoryarch 61, an an outer, or upper masonry arch 64, which arches sprinrespectively from the inner partition wals and the outer side wall, asl

shown, so that they may expand and contract independently. Between thesearches is a dead air space 6 3, affording heat insulation.

The torrid zone F, with its enclosed firing chamber F', will now bedescribed:

The outer walls 7 0, suitably reinforced, as before, with steel framing,are erected on a succession of masonry arches 71,l springing fromabutments 72, Fig. 4a .and over the top of the structure is carried amasonry arch 73, Fig. 14, springing from the reinforced upper portionsof these walls. The inner or lining structure is constructed of thehighest possible grade of refractory brick, and comprises Vside wallsmade hollow to enclose the longitudinal flues 57, having arched portions76 beneath, coinciding in arrangement with the outer arches 71, androofed over by a refractory arch 77 springing between the upper portionsofthe side walls, which portions are laterally reinforced against theouter side walls 70, as shown in Fig. 14. Between the arches 7 3 and 77is a dead air space 78, forming a heat insulation. Also,V betweenthe'lining wall and the outer wall, on each side, is an air chamber orcavity 79, forming normally a dead airspace on each side of the firingchamber. These several dead air spaces serve to insulate the interiorwalls, so as to preventloss of heat outwardly, thus protecting the outerwalls and promoting economy in the operation of the kiln.

The firing chamber F has an average width somewhat greater than that ofthe narrowed ortals 52 and 62, and is partially subdivided) at each sideto form a succession of compartmentsl 80, 80, in which, respectively,are located the Vfiring furnaces 90, 90, ivhich will be morespecifically described aber.

The compartments are, in part,- formed by piers 81, projecting inwardlyfrom the side walls 75 -and coinciding longitudinally with the outerarch abutments 72. Thus, the compartments coincide in' number andposition with the arches 71, which arches form a series of openings intothe respective internal compartments,throughl which openings the firingfurnaces may be introduced or removed. These arch openings in Vthe outerwall are rked 100, and those in the inner wall the inner furnacecompartments are l arched over at 102, to form furnace chamberscommunicating with the firin chamber, When the furnaces 90 are in p ace,as shown at` the right in Fig. 14, Apartitions or doors 91 close theouter arches 100, and vpartitions or doors 92 close the inner arches'101.

twelve firingfurnaces 90, six on eac side, but it will be understoodthat more or fewer may be dprovided, the important feature be# ing'tovide the heating meansinto units of suitable size to admit of readycontrol and to distribute the sources of heat along a considerableportion of the length of the tunnel, in order thatthe carloadsof' waresslowly advancing through the tunnel may be gradually raised intemperature in passing the successive furnace units. Each fur#refractory'bed portion 104 beneath the re-v spective compartments 80.Anti-friction rollers 9.6 or any other suitable means, may be provi edto facilitate the movement of ,carriages 94 on' the runwaysv95. Formoving the carriages, any suitable mechanical means may be provided,such as a screw 97 .engaged .by a .hand-Wheel 98 in a. well-.known man`By this means, the .several furnaces' ner. may be individually removedfrom their normal position', as shownat theright 'in Fig. 14, andcarried outwardly tothe posi- .tion shownat the left in' that ligure, topermit `of in ection, renewal, or repairs. When any rnace 1s .thusremoved, it is The kiln,y as Shown inthe. drawin has" highly importantto. be able to immediately close the opening into the ring chamber,because the normal closures 91 and 92 `have (been taken away; forjthispurpose, a shutoff gate is. provided for each furnace Aopening, thesegates being preferably constructed each as a vertically slidin' panel orslab 105, as shown in Fig. '14 which, in the normal-operation, iselevated to the position shown.. at the right in Fig. 14, or,immediately after the removal of a furnace unit, is lowered to theposition shown in the left of that figure. These gates thus move in thelateral dead air chambers T9. being preferably of a thicknessconsiderably less than the width of these chambers, so that, whenelevated, a suitable dead air space remains. The bottoms of the dead airspace between the arches 100, 100, are closed bytiles 106 which coincidewith the movable beds 94, and afford complete parallel side wallsbetween which the beds 94 may move. The movements of the gates may beperformed in any convenient manner, the means for this purpose showncomprising, for each gate, a vertical rod 107, the lower end of which isimbedded in the gate, while the portion above the gate may slide in aniron tube 108, built into the masonry. and the portion which, when thegate is lifted, isabove this tube, is screwthreaded and engaged by thethreaded hub of a wheel 109. having a bearing support 110 carried on theupper crossframing 111. By means of the gates 105, any furnace units maybe removed without interfering with the operation of the kiln, bymerely' droppingthe gate to close the opening and exclude cold air fromthe firing chamber. Gate 105 is thus lowered before` closure 92 iswithdrawn from openin 100, to prevent any ingress of cold air to t 'efiring chamber, and any loss of heat therefrom.

The firing dfurnaces 90 may be`of any suitable or known construction,according to the .fuel or source of heat which is to be used. For manyreasons, however, it is preferable to use electric furnaces, instead ofthose heated by gas or other fuel. The principal advantage of electricfurnaces is that. in their use, there is, or need be, no discharge intothe tiring -chamber of products of combustion s uch as mi ht injure thewares being fired. This avolds the necessity of-protecting the wares byen? closing them -in saggexs, or by constructing the kiln after themanner of mutle kilns, with a lining partition of thin refractorymaterial tol separate the tunnel chamber from the lateral chambers inwhich the combustion' or heating takes place. The use of such inutilepartition requires that the heating adjacent the tunnel chamber shall becarried to a higher temperature than that required in such chamber, inlorder to overcome the obstruction to the flow of heat occasioned by therefractory lining- 93 are hollowed, and are extended longitudinally ofthe tunnel, the opposite ends of each hearth being entered bylconducting bars or pencils 120 of carbon. 'preferably in graphite form,which pass through holes 121 in the hearths and through suitably linedholes 122 in the partitions 92, and are carried by carbon holders 123,which may pass through suitably lined orv bushed holes 124 in the outerpartitions 91. Each pair of these carbons constitutes a couple, to whichelectric current is conducted through any suitable conducting means,such as shown diagramatically in the form of wires at 125, in Figs; 4aand 14. Any suitable electric resistance material 99 is placed in t'hehollows of the hearths 93 and serves as the resistant connection betweenthe ends of the respective carbon pencils which enter opposite ends ofthe hearth, this resistant material being heated to incandesence by thepassageof the electric current.. As this material, broken or comminutedcarbon is preferable.

Theresistant material 99 and the carbon pencils 120 need occasionalrenewal and this lis conveniently accomplished by withdrawing thefurnace units, as shown at the left in Fig. 14, in the manner alreadydescribed.

The first cooling`zone G extends from the outlet portal 62 for asuitable distance, connecting, at its outlet end, through an expansionjoint, with the second cooling zone 'H. The enclosed portion G of the ftunnel chamber'constitutes a cooling chamber and is made wider andhigher than the dimensions of the restricted opening through the portal62, so that the inner walls 13G-of this chamber, and its roof lining orarch 131 (F ig. 10)- are at some distance away from the carloads ofwares. The outer -walls 132 are of masonry suported b y lan externalreinforcing steel raming, as before. At their entering end, these wallsjoin the portal 62 by an overhangingslip connection to form an expansionjomt in a manner which maybe suhstantially a duplication, of the jointbetween the Wall 51 and" inner and outer walls 53, 54 of the enteringportal 52, already described. Fig. 10 1s a section at this slip jointportion of the portal. being taken through the outer wall 133corresponding to 53) and inner Wall 134 (cor- .responding to 54),between which are formed the side connecting fines 65; the upperconnectin flue 66 is formedbetweenthe inner arch 7 and an outer arch136. Fig. 10.

The enclosing walls of the cooling zone G are traversed by a series ofair heatingfiues 140, which are best formed by the use, for the innerlining Walls, of hollow refractory tiles 141, and similar tiles 142 toform the inner portion of the arched top. The cuter masonry wall 132 andouter arched masonry roof 137 are shown as directly adjoining theselining tiles.

The expansion joint 145 between the first cooling zone G and the secondcooling zone H is formed, as best shown in Figs. 2", 3b, and 11, with anouter wall 146 and an inner or lining wall 147, which walls respectivelyembrace, with a slip connection, the side walls 151 of the cooling zoneH In the construction shown, the outer walls 146 form a continuation ofthe outery walls 132, and may be built of masonry integral therewith;the inner walls 147 are extended inwardly from the tile linings 141-tothe same extent as the inward projection of the portals 52 and 62. Thisinward projection thus -orms an additional portal, designated 148. Theouter and inner walls enclose a connecting iiue 160 on both sides andoverhead, which iiue serves to connect, on the onediand, the ends of allthe iues 140 traversing the zone G, and,on the other hand, a iue orflues 150, formed in the hollow or hollows, of the wall 151 and roofportion 152 of the zone H.

The second cooling zone H has its enclosed chamber H partially cut offfrom the iirst cooling chamber G', by the inter,- vening portal 148 inthe same manner-1 that the first cooling chamber is cut off from thefiring chamber. This zone H is best constructed of east iron plates orsections 153,

lin the same manner as the heating z one l?, except that, for thiscooling zone, 1t 1s preferable to extend the same construction over theroof, as shown in section in Fig. 12. Thus, the segmental iron platesare spaced apart, forming between them the iiue vspaces 150, the roofplates 152 being similarly separated, and forming between them theoverhead portion of this flue 150. rlhe side walls are built on afoundation 155 of masonry, which may be continuous with the foundation155, shown in Figs. 10 and 11. The iron walls are fastened, at bottom,to this foundation, the fastening being rigid at the end 'portionsnearest the zone G, the remainder of the side walls and top portionsbeing free to move longitudinally with changes of temperature, tor whichpurpose longitudinally-slotted bolt-holes may be used.

The final cooling or cool zone J is a duplicate of the inlet zone C,except that it is preferable to form the roof of segmental cast ironplates 162, instead of masonry or tile. The enclosed tunnel Chamber Jmay be an uninterrupted continuation of the chamber H', and of equalwidth.

t the junction 163 between the zones and J, the outer wall 151 of thezone H is discontinued, while the inner wall is contin'ued as the wall164 of. the yZone J. The space between these outer and inner walls isleft open, to constitute an inlet 161 Jfor admitting air to theintervening space or air heating flue 150.

The outlet end of the zone J is closed by a suitable door h, which maybe a duplicate of the inlet door.

The masonry construction throughout has its outer wall reinforced bysectional steel framing' 166 on the-sides and 167 overhead, this framingserving to resist the thrust of the archedmasory roofs in the mannerwell understood.

Having thus described the construction of the tunnel kiln, its operationmay now be understood.-

Following iirst `the flow of the air through the longitudinal lues orspaces It is understood that the kiln, having been brought into fulloperation, contains a train of cars, ,each fully loaded with Astacks ofwares in various stages' of heating and cooling, as will be more fullydescribed below.

'The air entering at 161 into the wall space or flue y150, surroundingthe cooling chamber H', flows slowly through this space into theconnecting flue 160, thence subdivides and traverses the longitudinalheating lines 140, formed within the tile lining 141 of the cooling zoneG; then, being united in the lateral iues and overhead equalizing Hue66, the already highly heated air is caused to flow through the twolateral fines 57 traversing the walls of the firing chamber F', thenentering the lateral lues 55 andl their connecting overhead fiue 56 and,being again subdivided, the air enters the multiple radiating pipes 50,through which it Hows Valong the opposite sides of the zone E; fromthese pipes, the air is discharged into lateral ues 42 and theiroverhead connection 44, and finally traverses the flue or air space 23between the walls of the zone D, the air ciirrents being finally unitedin the i'lue 25, from which they are drawn to the suction fan 26, bywhich the current of air is maintained. During this flow of the air, itis iirst hea-ted, by taking up the heat radiated from the carloads ofcooling wares in the cooling zones H and G, this heat being conducted toit through the lining walls of the chambers H', G; the highly heated airis then superheated while passing through the iiues: 57 traversing thelining of the tiring chamber; the air thus superheated then, in liowingthrough the radiating` pipes 50, gives out heat, which is radiatedl fromthese pipes to preheat ,the wares in the chamber E', and finally theair, now partially cooled, serves, while passing through the side flues23,'to initially heat the wares traversing the first. heat chamber D'.Thus, the air first takes up heat from the cooling Wares, and later, bya reversal of this function, givesout heat to preheat the Ienteringwares. In the tunnel chamber E', the

heated air is first carried throu' h the radiating pipes 50 (see Fig. 3)whi e these ipes are arranged Aclose, against the sides o the stackedwares; as the air loses heat, these pipes ecede from the sides ofthecars (see igt will be noted that the cooling air, which afterwardsbecomes the heating air, isnot vitiated by products of combustion, norin any way changed in character, so that, after being discharged fromthe fan, its remaining heat may be utilized for heating or drying, o1'for Vany purpose for which hot or warm air is available.

Now, following the progress of the wares through the kiln, it is to beobserved that these travel in the contrary direction to the tlow of air.The successive carloads of wares are practically continuous, the waresbeing so piled as to allow inter-spaces through which the heated airwithin the tunnel chamber may' circulate. While other wares or materialsmay be treated, the present description will assume that the wares areporcelain or earthenware, to be fired. The successive cars are run inthrough the entrance door into the warming chamber C and this doorclosed. This chamber C receives its heat entirelyy by means of a certainamount ot' circulation from the end of the second warming zone D, thewares slowly warming up as they pass over approximately 2O feet oftrack, and then entering the second heating chamber D', where they firstreceive direct radiation from the side walls of the tunnel, where thelatter are heated from the air circulating through the lues 23, on itsway t0 thc fan 26, at which time the air has given up nearlyv all theheat it had gathered from the cooling zone and torrid zone. The ironwalls of the tunnel in this' section D radiate the heat directly to thewares. this etiect being accompanied by convection by reason of thecirculation of air in the tunnel chamber being upwards along both wallsto a meeting of the lrespective cuirents at the top, and thence downwardt rough the wares to the floor of the `car. and outward in bothdirections to the walls; this' rotary current being continuous andspontaneous. The tianged structure 0f the walls in this section D of thetunnel assists in breaking up the ascending air currents. and alsoprovides increased radiating surface. It desired, the outer iron wallsmay be insulated b v an exterior covering of brick work or insulatingmaterial, asis Common.

The ware train is kept moving continuously or intermittently, and at asuitable rate throughout the length of the tunnel kiln. Continuousmovement is preferred, and at a rate such that each car moves its ownlength in about one hour. Asthe'cars progress through the heating zonel),v they encounter continually hotter walls, from which there is aprogressively higher heat radiation.v In time, each car passes lfrom theheating chamber D into the final preheatin chamber E, where the tunnelchamber su denly widens. In the progress of the carsthrough this chamberE', the Wares receive a continually incl/easing hea-t radiation from thecast iron radiating pipes .50, which, at the entering end, are somewhatseparated laterally from' the loads of wares, and which graduallyapproach these as the cars advance. At about halfway through thischamber, the outer brick wall of the tunnel is reinforced by a tirebrick lining 35 on the` side walls, and 38 at the roof, as, throughoutthe after portion of this chamber, the heat is elevated to a degree thatwould be injurious to common brick. Throughout this chamber, the sameconvective lateral circulation of air within the tunnel chamber andthrough the wares takes place, except that, as the heat is constantlybecoming more intense, this circulation is probably more rapid andeffective. In the final portion of this chamber, the radiatingy pipesare brought as close to the sides of the loads of wares as ossible, inorder to make this lateral circulation the most effective.

In this section E of the tunnel is introduced an important improvementin such kilns:

The Ware entering the kiln is at a stage of process called chalk white;that is,`the clay is predried to a pointv where there isno apparentmoisture present but molecular moisture remains. and, as the carprogresses in the kiln, is liberated from the ware and is present assuperheated vapor in the circulating air surrounding the ware train. Itis necessary to remove this moisture; and for that purpose and also forthe purpose of replenishing oxygen withinthe kiln, advantage is takenota certain amount of air leakage at the doors at either end. also airleakage into the tunnel ata number of spy holes and a leakage in theside walls about the tire hearths in the torrid zone. A stack 170 isbuilt over the tunnel at approximately one-third of the length of thepreheating chamber E forward of the entrance to the torrid zone, andbeing connectedv directly with the interior ot' said chamber', createsan updraft which drawing on the tunnel interior produces a slow currentfrom lboth ends, the current from the entranceend carryingI with it themolecular moisture vapor which, being always lighter than the normal airof the tunnel, readily finds its outlet to the stack, `while the currentfrom the exit end, aiding primarily in cooling the ware on its waythrough the tunnel t0 the stack, takes up the peak heat of the torrid izone and entering the preheating chamber tal the carload of wares issubstantially cutYV off from external sources of heathfora suitable'time (preferably at least one hour), so

that during this time any irregularity in preheating of differentportions of the wares 1s corrected` by4 mutualradi'ation and con-Yvection, thusmc'complishing an equalization of the preheating throughouttheY load of wares. s

While in the torrid zone or firing chamber, the ware train is betweentwo rows of direct ire from the furnaces 90, 90. The advancing Ware justenterin from the preheati'ng chamber receivesv t e direct heat from thefirst pairfof furnaces, and thereby is gradually elevated intemperature. Passing,l next, the second pair of furnaces, it is fartherelevated in temperature, attaining its maximum temperature at thejfourthpair land maintaining this temperature past the thand sixth units (thisaction being modied in theY case of a greater or lesser number of' suchunits). During the latter part of their passage through the tiringchamber,

the waresare at incandescence, and, while passing throughY the outletportal 62, the lining of which is incandescent, this incandescence ismaintained, thus giving the wares a steady soak, Ywithout tire, for thatperiod. This static heat treatment in the n outlet portal repeats in amanner the heat equalization occurring in the inlet portal, so. that-ifthe wares are unequally incandescent, or at unequal temperatures, thisinequality is corrected by mutual radiation and by' convection.

On leaving this outlet portal, the wares 'i enter the first coolingchamber G', in which the heat radiated from the wares is taken upslowly1 by the hollow tile Wall and arch construction, and transmittedto the air circulating through the tlues formed in these hollow tiles.As the ware ytrain advances, the wares continue to'give up heat thus tothe absorbent walls, the convective action now occurring by circulatingup throughl the wares to the roof ,and down the sideso-the tunnel to the'iioorof the car, thence returning to the roof; and, because otthis`circulation andlof the absenceof any'perceptible draft through thetunnel, the wares cool gradually and equally, thus avoiding danger ofbreakage through unequal contraction.

,This action proceeds progressively during the slow advance of thecarloads of wares ation of air through thetunnel chamber.

On entering the second cooling chamber H', the wares continue to giveout heat which, conducted through the inner iron Walls 'of this chamber,is taken up by the cool air circulating throu h the hollow space or iue150 'in the side wa ls and roof. This construction rovides for ready andrapid absorption o heat from the walls so that, Whenthe latter havereached the end of this section at 163 and enter the single wallconstruction of the nal cool section J, the wares will have cooled tosuch 'an extent that, on their final passage through this section for adistance of about 2O feet (taking some 3 hours), the wares undergo atempering rocess under cover which puts them in con ition for safeexit*V to the open air. Finally, as each car reaches the exit opening,the end door b is opened and the car run out and the' door 'then againtightly closed. Y*

The total length of the tunnel kiln and the roportionate lengths of thesuccessive heating. zones of the torrid zone and of the cooling zonesare matters which may be approximately arrived at by computation asedupon past experience' with tunnel kilns of other types, but which may befinally determined as to the best proportions only after a sufficientdegree off'experience in the use of tunnel kilns of this improved type;and these proportions will be subject to variance according to therequirements Yof ditl'erent kinds of wares or different heat treatmentstor which the kiln is to be used.

An important feature of the improved construction herein set forth isthe provision 4of means forY protecting the tunnel structure against theinjurious or destructive effects of expansion and contraction. Toprovide for expansion and contraction in longitudinal direction, thekiln is divided longitudinally into sections which, in their nature, aresubject'ito varying temperatures in use, and, consequentlygtovaryingdegrees of expansion and Ycontraction while heating up andcodling down before and after a period of practical serviceL Theconstruction of expansion joints at the meeting places of thesesuccessive sections, as already described, makes adequate provision forallowing for theeftects of expansion in this direction.

llO

Lateral and vertical expansion is also provided for; but, as there islittle, if any, lateral movement of the walls or of the basefoundations, the roof arches are the only members to be considered; and,since the thrust of the arches is always taken up against the steelreinforcement, it follows that the only movement due to expansion wouldbe a bowing upwardly of the crowns of the successive arches. It is,therefore, seen that the tunnel structure is free to expand from itsbuilt dimensions to anew heated dimension, and, when cooled at any time,its dimensions are diminished from its expanded position,l this beingtaken up in the expansion joints and by, in some cases,

the opening of joints in the side walls, while the arch crown will lowersomewhat in cooling; all parts of the structure, however, resuming theirfixed expanded position when again heated.

ln order to provide for ready inspection of the tire hearths and of thewares in their progress through the firing chamber, suitable peep holesare provided in the sides and at thev ends of this chamber.l The lateralpeep holes are best formed at 171, F igs. 2a and 4;, that is, throughthe stopperwalls or doors 91, 92, pertaining to the individual furnaces.End vpeep holes 172 are formed on opposite sides and at opposite ends ofthe firing chamber (see Fig. 3a.), these peep holes passing through endwalls 173 forming the inner masonry members of the portals and G2respectively. The arched recess 58. already referred to in describingthe portal 52, and corresponding recess 68 pertainingto porta-1162,afford compartments opening externally which may be entered to make useof these spy holes. The provision of these -holes makes possible a readyinspection of the fire hearths from either end, and also enables avision of the passing cars. As the spy holes at either end will sweep atield of more than one-half the length of the tire chamber, it followsthat the cars and wares in 'the firingchamber are always under visualinspection.

The improved'tunnel kiln herein set forth is designed and ideallyadapted to maintain an intense heat in the torrid zone and a practicallyquiescent firing chamber from which no material loss of heat occurs;with the result that, when, in the original firing up of the kiln, theheat once reachesits peak, it may be maintained over long periods atrelatively low cost of operation. In the firing chamber, thelongitudinal flow of heated air, due to minute leakage through the enddoors, furnace joints, peep holes and other interstices, is so slow thatsuch longitudinal flow becomes negligible so far as a lfects thepractical quiescence of the at mosphere within this chamber.

Bv referring to this atmosphere as quiescent. I do not negative thenormal rotative circulation of air in transverse planes, by which theuniformity of heating and the equal incandescence of the waresthroughout the stack thereof, is assured. Nor do I ignore the extremelyslow flow of air, in volume equal to the aggregate in-leakage, towardthe stack 170, already described.

It will be evident from the foregoing description, that the inventionmay be modified in construction, proportions and details in many ways,according to local conditions and the specific uses to which the tunnel'kiln is to be applied. I desire it understood that all suchmodifications which are within the scope of the appended claims are to.be deemed within my invention.

`What' I claim is:

1. A tunnel kiln having a continuous tunnel chamber and successive carstraveling therethrough, the kiln comprising a heating zone, a torridzone, and a cooling zone, having end doors, and the inlet and outletportions of the tunnel chamber formed of minimum cross-section closely:approximating that of the carloads of stacked wares under treatment,lwhereby to substantially close the end port-ions of the tunnel and`prevent inflow of air toward the torrid zone, and the firing chamber atthe torrid zone of greater cross-section, and having a dead airinsulation surrounding the tunnel chamber, whereby when once heated tooperative incandescence the..=.k iln yconserves heat and permitseconomic'operation, an-d means for absorbing heat radiated'A from theWares traversing the cooling zone, conveying such heat past the firingchamber, and radiating it in the heating zone to preheat the Waresthere- 2'. A tunnel kiln according to claim 1, the firing chamber beingheated by multiple electric furnaces under independent control, wherebythe advantages of electric heating` are rendered available undereconomic conditions.

3. A tunnel kiln having a tunnel chamber for the passage of carstraveling therethrough, comprising a heating Zone, a torrid zone. and acooling Zone, the torrid zone formed as a firing chamber with a doublearched roof and dead air insulation in such roof and in its side walls,and expansion joints of overlapping refractory masonry at the junctionof the torrid zone and the heating and cooling zones.

4. A tunnel kiln formed with an expansion-joint where the torrid zonejoins a portion of the kiln subject to less extreme temperature changes,and having a transverse chamber coinciding with such expansion joint. v

5. A tunnel kiln structurel comprising a torrid zoneforming the firingchamber, and preceding and succeeding zones which are normally subjectedto lower temperatures, such zones partially separated by portals on bothsides of the firing chamber adapted to closely enclose the carloads ofwares to substantially cut off circulation of gases between such zones,and of a length such as to enclose a carload mass of wares, the tunnelstructure formed between the torrid zone and the adjacent zones, withrefractory masonry portions forming an expansion joint to enable therespective sections of the structure to expand or contractindependently.

6.- A tunnel kiln structure according to claim 5, having longitudinalfines through the masonry walls, and having' transverse chambers at theexpansion joints connecting the flues on opposite' sides of such joints.

7. A tunnel kiln structure divided transversely into longitudinalsections which are subject to diverse temperatures, such sectionsmeeting with a double sliding joint. and a lateral flue chamber at suchjoint, whereby the movements due to temperature changes are taken up insuch lateral chamber.

8. A tunnel kiln the torrid zone of which joins the preceding andsucceeding portions of the kiln with expansion joints of -refractorymasonry, having transverse chambers at the expansion joints, andlongitudinal ues in the masonry walls, the flues on opposite sides ofsuch joints communieating through said chambers. Y

9. A tunnel kiln the torrid zone of which is formed with a firingchamber partially separated from the preceding and succeeding zone byportals adapted to closely enclose t-he carloads of wares, such portalsof a length such as to enclose a carload mass of wares and hold them inthermostatic condition for a timesufficient to effect equalization oftemperatures.

10. A tunnel 'kiln having a heating zone and torrid zone, the tunnelchamber between such zones being contracted to form a portal closelyapproximately the cross-section of the carloads of wares, so as tosubstantially cut off circulation between such zones, and such portal ofa length suficient to enclose the moving carload of wares and hold themin thermostatic condition for such time as to effect equalizationoftheir temperatures.

11. A tunnel kiln having a torrid zone and a cooling zone, the tunnelchamber between such zones being contracted to form a portal closelyapproximating the crosssection of the carloads of wares, so as tosubstantially cnt off circulation between such zones, and such portal ofa length sufficient to enclose the moving carload of wares and hold themin thermo-static condition for such time as to effect equalization oftheir temperatures.

12. A tunnel kiln having a heating zone, a torrid zone and a coolingzone, the torrid zone formed as a firing chamber of greatercross-section than the traveling carloads of wares, and such chamberformed with lateral compartments of greater width, independent portableheating units in such compartmentson opposite sides of the carloads,lateral openings to permit the remaval of any of such heating units, andmeans for closing such openings-- 13. A tunnel kiln the torrid zone ofwhich is provided on opposite sides of the tunnel chamber withsuccessive heating units, and means for permitting the removal of anyone unit independently lof the others, and means for closingcommunication with the chamber upon the removal of such unit.

14. A tunnel kiln the torrid Zone of which is formed on opposite sideswith successive furnace compartments, and independent furnace units inSuch compartments.

15. A tunnel kiln the torrid zone of which is formed on opposite sideswith successive furnace compartments, and independent furnace units insuch compartments, such units being individually rcmovable.

1G. A tunnel kiln the torrid zone of which is formed on opposite sideswith successive furnace compartments, and independent furnace units insuch compartments. such units being individually removable, and meansfor closing off an)v cornpartment upon the removal of its furnace unit.

17. A tunnel kiln the torrid zone of which is formed on opposite sideswith successive furnace compartments, and independent furnace units insuch compartments, such units being individually removable, carriagesfor the individual furnace units, and closures on said carriages for theopenings through which the units are removable.

18. A tunnel kiln according to claim 17, with independent closing meansfor shutting off any compartment when the furnace is removed.

19. A tunnel kiln having at its torrid zone on opposite sides a seriesof successive independent electricV furnaces, with means for controllingthem individually, and means whereby said furnaces may be independentlyremoved and replaced.

20. A tunnel kiln having at its torrid zone on opposite sides aplurality of electric furnace units, and means for controling thelindividual units independently, with openings through which such unitsare independently removable, and means for closing such openings.

2l. A tunnel kiln having at its torrid zone a plurality of electricfurnace units, each unit independently removable, the kiln havingopenings for permitting their removal and movable doors for closing suchopenings 22. A tunnel kiln the chamber of which at itstorrid zone isformed with successive compartments, exterior openings communicating`with such compartments, doors for closing such openings, and electricfurnace units movable through such openings into such compartments.

23. A tunnel kiln having atl its torrid zone a plurality of electricfu-rnace units, each unit imlepemlently removable. and carriages` torsuch furnace units.

24. A tunnel kiln having at its torrid zone a plurality of electricfurnace units. cach unit independentlyremovable, and carriages` for suchfurnace units. the kiln having openings for passing such carriages andunits. and doo-rs for closing such openings.

A tunnel kiln having at its torrid zone a plurality of independentlyremovable electric furnace units` each such unit coinprising a hearth,carbon pencils leading to such hearth, and resistant material on saidhearth bridging Said pencils.

26A A kiln according to claim 22, having lateral runways through saidopenings, and carriages for the furnace units traveling` in suchrunways.

i 27. A tunnel kiln having at its torrid zone a plurality of electricfurnace units, each unit independently removable, and carriages for suchfurnace units, the kiln having openings for p'assinof such carriages andunits, and doors for closing such openings carried on such carriages toclose them when the units are in place. and separa-te means for closingsuch openings when the units are removed.

28. A tunnel kiln comprising a heating zone a torrid zone and a coolingzone, means for transmitting heat radiated bly the cooling wares topreheat the wares in the heating zone with electric furnaces for-heatingthe. torrid zone, whereby discharge of burning gases into the kiln isavoided, the kiln having suction means fo-r drawing air from the tunnelchamber at a point in the heating zone` the. ratbf suction graduated toremove v-apor being evaporated from the preheated 'wa-res Withoutmaterial indraftl of hot gases into the heating zone from the torridzone. .l

29. A tunnel kiln comprising'a heating zone, a torrid zone and a coolingzone, with electric furnaces for heating the torrid zone` wherebydischarge of burning gases into-the kiln is avoided, the kiln havingsuction means for drawing air `from the tunnel chamber at a pointclosely pre-ceding thc torrid zone. its rate of suction graduated to be.only sullicient to remove inleaking air, but not sullicient to impairthe normal convection etlect in the torrid zone chamber. .o

30. A tunnel kiln comprising a heating zone` a torrd zone and a coolingzone. the torrid zone and heating zone partially .separated by a portaladapted t-o closely enclose the carloads of ware-s to substantially cutolil circulation of gases between .such zones. and of a` length such asto enclose a carload mass of wares, with electric furnaces tor heatingt-he torrid zone. whereby discharge of burning gases into the kiln isavoided. the kiln having suction means for drawing air from the tunnelchamber in the. heating zone.` its rate of suction graduated to be onlysutiicient to remove inleaking air. but not snllicient to prevent thespontaneous lat- 'i eral circulation of, air within the tunnel chamber.

3l. A tunnel kiln comprising a heating zone.. a torri/d zone and acooling zone. the torrid zone and heating zone partially separated by aportal adapted to closely enclose the carloads of wares to substantiallycut ofi' circulation of gases between such zones. and of a length suchas to enclose a carload mass of wares, with electric furnaces for -fheating the toi-rid zone, whereby discharge of burning gases into thekiln is avoided, the kiln having suction means for drawing air from theheating zone ot' the tunnel chamber at a point closely preceding thetorrid zone, graduated to operate at a rate only sufficient toi'emoveinleaking air. whereby such air circulates slowly through thecooling chamber, the torrid chamber, and into the heating chamber.

32. A tunnel kiln having a heating zone, a torrid zone and a 'coolingzone with electric furnaces for heating the torrid zone Withoutdischarge of combustion gases thereinto, the tunnel chambers contractedat the junction of the torrid zone with the heating and cooling -zonesto form portals closely approximating the cross-section of the carloadsoiwares, so as to substantially cut off circulation between such zones,and such portals of a length suflicient to enclose the moving wares andhold them in thermostatic condition for such time as to effectequalization of their temperatures, and suction means'for drawing airfrom the heat- 120 ing zone at a rate sufficient only to removeinleaking air, whereby to cause aslow circulation of air longitudinallyof the torrid zone.

33. A tunnel kiln having a preliminary heating zone, an intermediatetorrid zone. and a final cooling zone. the torrid zone having insulatingwalls to retain the heat, and air fines therein insulated from theexterior Walls,

and the preheating zone and cooling zone l having lining walls insulatedfrom the exterior walls, and air flues'in their lining walls, andmearis'pfor circulating air first through the flues vof the 'coolingzone to absorb heat from the cooling wares, then through said iuespassing the torrid zone, and'finally through the flues of the heatingZone to impart to the: wares approaching the torrid zone the heat takenup by the air.

34. A tunnel kiln according to claim 33, the lues passing the: torridzone having no communication with the heating means.

35.*A tunnel kiln according to claim 33, the flues passing the torridzone being formed in the lining walls thereof remote from. the source ofheat.

36. A tunnel kiln according to claim 33, the lues in the heating zonebeing formed in the side liningv walls of the kiln.

37, A tunnel kiln according to claimr33, the means for circulating theair being a suction fan applied at the delivery from said 'flues in theheating zone. i

38. A tunnel kiln according to claim 33, the lines passing the torridzone having no communication with the Yfiring chamber.

39. A tunnel kiln the firing chamber of vwhich has contracted portals iat opposite ends, with lateral recesses in such portals, and peep holesopening from such recesses into the ends of the chamber.

Y40. The torrid zone of a tunnel kiln having yits sides formed withsuccessive abutments and arches thereover, side walls above said arches`an arched roof, and lining walls similarly arched to form successivecompartments at the sides of the firing chamber, and removable closuresfor th lateral arched openings. Y i

41. A tunnel kiln having lateral openings int-o its firing chamber,movable doorsl for normally closing said openings, and extra closuresmovable into said openings before the removal of said doors, whereby toprevent'ingress of cold air. Y

42. A tunnel kiln having lateralY openings into its firing clamber,laterallyY removable furnace units having portions normally closing suchopenings, and extra closures movable into said openings before theremoval of said normal closures. l

43. A tunnel kiln having lateral openings into its firing chamber,laterally removable furnace units having portions normally closing suchopenings, a movable bed carrying each such furnace unit and closure, andan extra closure for each opening, movable thereinto before the removalof said normal closure.

44. A tunnel kiln having its torridzone formed with inner and outer sidewalls, with dead air spaces between them, and having lateral openings inits side walls, furnace units accessible through said openings, andspaced closures for said openings having spaces between them formingcontinuations of said dead air spaces in the side walls.

In witness fwhereof, I have hereunto signed my name. Y

WINFIELD E. HNSDALE.

